Controllable fuses which utilize a heater element are known. In such fuses when an electrical signal is applied to the heater element sufficient heat is developed to result in interrupting a circuit connection between circuit terminals which are separate from the heater element. One such device is manufactured by Therm-0-Disc of Mansfield, Ohio, U.S.A. This device appears to utilize a soldered connection between two primary terminals wherein a spring will open this soldered connection upon the solder reaching a molten state. A separate heater coil is then wound around an insulating sleeve that surrounds the solder connection. Upon application of an external electrical signal to the heater coil, sufficient heat is provided such that the solder reaches a molten state and the spring then results in providing an open circuit between the two primary terminals. This type of fuse is typically a nonresettable fuse. Such fuses are utilized in various "fail-safe" applications such as an anti-lock brake system (ABS). In case of a failure such a fuse will provide an open circuit which results in a vehicle reverting to conventional, as opposed to anti-lock, braking control.
Fuses such as the Therm-O-Disc device described above, typically utilize a large number of parts and do not lend themselves to low cost production techniques. Also, in such devices, the heater coil must be wound around the insulating sleeve and the thermal coupling provided by this insulating sleeve may not be consistently reproduced resulting in variable performance or response times for the resultant fuse. Also, typically such fuses do not have any redundancy structure so if the heater fails or if the wrong signal is provided to the heater, the fuse fails to operate properly.